A cochlear implant is an electronic device that may be at least partially implanted surgically into the cochlea, the hearing organ of the inner ear, to provide improved hearing to a patient. Cochlear implants may include components that are worn externally by the patient and components that are implanted internally in the patient.
External components may include a microphone, a processor, and a transmitter. Cochlear implants may detect sounds via an ear level microphone that conveys these sounds to a wearable processor. Some processors may be worn behind the patient's ear. An electronic signal from the processor may be sent to a transmission coil worn externally behind the ear over the implant. The transmission coil may send a signal to the implant receiver, located under the patient's scalp.
Internal components may include a receiver and one or more electrodes. Some cochlear implants may include additional processing circuitry among the internal components. The receiver may direct signals to one or more electrodes that have been implanted within the cochlea. The responses to these signals may then be conveyed along the auditory nerve to the cortex of the brain where they are interpreted as sound.
Some cochlear implants may be fully implanted and include a mechanism for measuring sound similar to a microphone, signal processing electronics, and means for directing signals to one or more electrodes implanted within the cochlea. Fully implanted cochlear implants typically do not include a transmission coil or a receiver coil.
Internal components of such cochlear implant systems typically require electrical power to operate. Thus, a power supply is typically included along with the other internal components. However, performance of such power supplies often degrades over time, and the power supply may require replacement. Additionally, processing circuitry technology continues to advance quickly. Improvements to processing technology over time may render the processing technology in the implanted processing circuitry outdated. Thus, there may be times when it is advantageous to replace/upgrade the processing circuitry.
However, such replacement procedures can be difficult. The location of the implanted internal components is not the most amenable to surgical procedures, and tends not to fully heal after many incisions. Additionally, replacement of some components, such as a signal processor, can require removing and reintroducing components such as electrical leads into the patient's cochlear tissue, which can be damaging to the tissue and negatively impact the efficacy of cochlear stimulation.
Additionally, different challenges exist for communicating electrical signals through a patient's body. For example, safety standards can limit the amount of current that can safely flow through a patient's body (particularly DC current). Additionally, the patient's body can act as an undesired signal path between different components within the body (e.g., via contact with the housing or “can” of each component). This can lead to reduced signal strength and/or undesired communication or interference between components. In some cases, electrical signals may even stimulate undesired regions of the patient's cochlear tissue, interfering with the efficacy of the cochlear implant.